HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH SEARCH RESULT		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 96/4/1393    most recent 01040.2003v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Klentrou, P. Articles by Plyley, M. Search for Related Content PubMed PubMed Citation Articles by Klentrou, P. Articles by Plyley, M.

Temperature regulation during rest and exercise in the cold in premenarcheal and menarcheal girls

¹Faculty of Applied Health Sciences, Brock University, St. Catharines, Ontario L2S 3A1; ²Children's Exercise and Nutrition Centre, Department of Pediatrics, McMaster University, Hamilton, Ontario L8N 3Z5; and ³Faculty of Physical Education and Health, University of Toronto, Toronto, Ontario, Canada M3J IP3

Submitted 29 September 2003 ; accepted in final form 8 December 2003

Temperature regulation during exercise in the cold was examined in 13 adolescent female individuals, aged 13-18 yr. Six girls with established menstrual cycles comprised the eumenorrheic menarcheal (EM) group, and seven nonmenstruating girls comprised the premenarcheal (PM) group. During the first visit, maximal oxygen consumption (O_{2 max}), height, weight, and percent body fat were measured. The second visit included a determination of metabolic rate in thermoneutrality (21°C), consisting of a 10-min rest period and 20 min of cycling (30% of O_{2 max}), and a cold test (5°C, 40% humidity, <0.3 m/s air velocity) involving a 20-min rest period and 40 min of cycling (30% of O_{2 max}). Subjects in the EM group were tested twice in the chamber: once during the follicular and once during the luteal phase. Heat production per kilogram in thermoneutrality and in the cold was significantly (P < 0.05) higher in the PM compared with the EM girls. However, the PM girls had a significantly (P < 0.05) lower core temperature in the cold than the EM group. PM girls also had a significantly higher body surface area-to-mass ratio compared with the EM girls. Although percent body fat between groups was not significantly different, within the PM group percent body fat explained 79% (P < 0.01) of the variance in the decrease of core temperature. There were no menstrual phase-related differences in temperature regulation in either the thermoneutral or cold environment. In conclusion, menstrual phase does not influence temperature regulation in female individuals during adolescence. EM girls had lower metabolic heat production but maintained their core temperature more effectively in the cold than did the PM girls. This thermoregulatory difference between PM and EM girls is mainly a function of geometric differences with maturation-related peripheral vasoconstrictive differences maybe limiting the effectiveness of the mechanism of increased heat storage in younger female individuals.

reproductive status; menstrual phases; core temperature; heat production; surface area-to-mass ratio